Feedback Control in Quantum Optics: An Overview of Experimental Breakthroughs and Areas of Application
Figure 1
Depiction of measurement-based (a) and coherent (b) feedback loops. In (a), the output system, after having interacted with the system, is measured, and the classical information contained in the measurement outcome is then used to affect the evolution of the quantum system (typically by modifying the Hamiltonian); in (b), the output quantum state is coherently manipulated (typically by a unitary operation), and then fed back into the quantum system as an input state through a coherent coupling.
